chapter 9 - the Visual System Flashcards
The electromagneticspectrum
gamma
X-ray
UV
VISIBLE LIGHT 400nm - 700nm
Infared
micro
radio
the longer the wave length, the ____ dangerous it is to us
less
what part of the spectrum do insects
visible light and UV
what part of the spectrum do snakes see in
infared
what part of the spectrum can birds see in
UV and visible light
the shorter the wave length, the ____ dangerous it is to us
more
how does the eye convert light into a signal?
- enters cornea (protection)
- through pupil (hole)
- Lens (focuses light)
- Retina (cones and Rods)
- Fovea (on retina)
which part of the eye dilates and constrict the pupil
iris
Myopia vs. Hyperopia vs. Presbyopia
MY-opia: can’t see far
HYPER-opia: can’t see close (lifelong)
PRESBY-opia: can’t see close (old-age)
Cells of the retina from back to front
RH BAG
ganglia (collect the signal)
amacrine (modulates the signal to detect motion)
bipolar (transmits signals from R&C)
horizontal (enhancing contrast and edge detection)
receptors (rods and cones)
describe the distribution of rods and cones acroess the retina
cones: heavily on the Fovea (high-res) 0*
rods: densist at 20* and dcreases towards edges (since periphral is mostly for motion detection, not high-res)
S-cones detect ____ at ___ nm wavelegnth
M-cones detect ____ at ___ nm wavelength
L-cones detect ____ at ___ nm wavelength
blue, 440
green, 540
red, 575
Scotopic vs. Photopic Vision
Scotopic
-nightime (rods)
-lower wavelengths
-monochromatic
-peripheral retina
Photopic
-daytime (cones)
-Higher wavelengths
-Full colour vision
-fovea
What is the purkinje shift?
As the environment becomes dimmer, your visual system transitions from cone-dominated photopic vision to rod-dominated scotopic vision.
Since rods are more sensitive to blue-green wavelengths and insensitive to red, colors like red and yellow start to fade.
At the same time, colors in the blue-green range might seem more noticeable or brighter because that’s where rods are most sensitive.
what do M and P cells have to do with the optic nerve?
M cells, “I easily see something is moving fast! I have no idea what it could be”
P cells, “hard to see what it is because its moving so fast but it looks like its a red ball”
optic chiasm
optic chiasm is a crucial structure in the visual pathway where some of the axons from the optic nerves cross over to the opposite side of the brain
Geniculostriate Pathway: location, response, example
main pathway:
(location) Lateral Geniculate Nucleus LGN
(response) visual awarness / fine details
(example) reading a book
RETINOTOPIC MAP: each area on the retina has a coresponding place in the LGN
Tectopulvinar Pathway: location, response, example
secondary pathway:
(location) visual signals to Superiour Colliculus (tectum)
(response) automatic responses / reflexes
(example) moving when a ball comes flying at you
Retinohypothalamic Pathway: location, response, example
secondary pathway:
(location) visual signals to Superiour Colliculus SCN
(response) cicadian rhythms / biological clock
(example) sleep schedule
what are the Parcocellular and Magnocellular areas of the LGN
Parvocellular 3, 4, 5, 6
P-cells (Slow, good for static images)
Magnocellular 1 , 2
M-cells (Fast, good for detecting motion)
Who studied receptive fields of neurons along the visual pathway?
Hubel and Wiesel
why does visual input go from LGN to the Occipital Lobe?
ganglia in the LGN projects a blurry outline
the Occipital Lobe creates a high-res and fine detailed image
the central part of the visual field is represented at the ____ of the brain
back
the peripheral areas of the visual field are located more _____
anteriorly (closer to middle compaired to back)
